1. The Field of the Invention
Embodiments of the invention relate to the field of semiconductor lasers. More particularly, embodiments of the invention relate to a vertical cavity surface emitting laser integrated with an electro-absorption modulator.
2. The Relevant Technology
Computer and data communications networks continue to proliferate due to declining costs, increasing performance of computer and networking equipment, and increasing demand for communication bandwidth. Communications networks—including wide area networks (“WANs”), local area networks (“LANs”), metropolitan area networks (“MANs”), and storage area networks (“SANS”)—allow increased productivity and use of distributed computers or stations through the sharing of resources, the transfer of voice and data, and the processing of voice, data and related information at the most efficient locations.
As the demand for networks has grown, network technology has developed to the point that many different physical configurations presently exist. Examples include Gigabit Ethernet (“GE”), 10 GE, Fiber Distributed Data Interface (“FDDI”), Fibre Channel (“FC”), Synchronous Optical Network (“SONET”) and InfiniBand networks. These networks, and others, typically conform to one of a variety of established standards, or protocols, which set forth rules that govern network access as well as communications between and among the network resources.
In some optical networks, there are certain requirements related to transmission distance and data rate. When these requirements are relatively high, edge-emitting Distributed Feedback Lasers (sometimes with external modulators) are conventionally used because of the difficulties in using comparatively less costly VCSEL lasers. For example, as the data rate for an 850 nm VCSEL is increased to 10 Gbits/second and greater, the aperture size of the VCSEL is reduced to less than 10 micrometers to improve speed. Unfortunately, the small aperture size of such a VCSEL reduces the reproducibility and the reliability of the VCSEL.
In addition, a conventional VCSEL often has a high RC constant. The RC constant can limit the performance of the VCSEL to around 10 Gbit/second. High data rate applications would therefore require an array of VCSELs operated in parallel, which would significantly increase system cost. Further, conventional VCSELs at higher wavelengths such as 1.31 micrometers or 1.55 micrometers, are relatively expensive and often have reliability issues. As a result, applications associated with wavelengths such as 1.31 micrometers or 1.55 micrometers use edge-emitting FP (Fabry Perot) and DFB lasers. Links over very long distances typically require light sources operating at near 1.55 micrometers due to the low loss of the single mode fiber at this wavelength. Directly modulated-lasers including DFBs and VCSELs that operate at these wavelengths experience chirp problems that prevent their use at higher data rates and over longer distances. To reduce the chirp of the transmission, electro-absorption modulator edge emitting lasers (EMLs) are used where the optical power of the DFB laser section is maintained constant while the data signal is inserted through the electro-absorption modulator (EAM) section.